2023 LZ0 AT4 electronics, trans, dash goes suddenly goes crazy, check engine, will not shift - truck goes insane

[Wakinvol]

Also, I only bought the 1200 mile one because they sold the 0 mile one in the same color before I could put a deposit down!

 

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[FrankAbagnale]

I bought my 23' AT4 in Feb and had this issue happen to me in May. I went to the store last Sunday, and the same thing happened. I had to have it towed to the dealership.

Pretty irritating that this seems like it's going to happen every few months, but the worse part for me is no dealership can get me in! It's been sitting at the dealership for a week now, and they haven't even pulled it in to look at it. They are telling me they might not have time for another week. I called multiple other dealers, and they all said the same thing. So much for a warranty if they can't even service them!

These guys could care less as well. They keep telling me I should have made an appointment! Who the hell makes an appointment for a brand new truck to break down and need to be towed in?! I told them to go ahead and make an appointment for me every month, just in case.

I love the look of the truck, the diesel has been getting great fuel economy, but I'm over here starting to research the Tundra. Not sure if I will make the switch, but I can't keep going through this.

Bought mine at Laura as well. But, having it services in my town in MO.

 

[Wakinvol]

I bought my 23' AT4 in Feb and had this issue happen to me in May. I went to the store last Sunday, and the same thing happened. I had to have it towed to the dealership.

Pretty irritating that this seems like it's going to happen every few months, but the worse part for me is no dealership can get me in! It's been sitting at the dealership for a week now, and they haven't even pulled it in to look at it. They are telling me they might not have time for another week. I called multiple other dealers, and they all said the same thing. So much for a warranty if they can't even service them!

These guys could care less as well. They keep telling me I should have made an appointment! Who the hell makes an appointment for a brand new truck to break down and need to be towed in?! I told them to go ahead and make an appointment for me every month, just in case.

I love the look of the truck, the diesel has been getting great fuel economy, but I'm over here starting to research the Tundra. Not sure if I will make the switch, but I can't keep going through this.

Bought mine at Laura as well. But, having it services in my town in MO.

Laura can KMA but that’s another issue all together. It’s a simple fix when they get it in. Just find a good dealership and give them the story. Also call GMC customer support.

 

[FrankAbagnale]

Just a follow-up on my issue. My truck was in the shop for two weeks. The service experience was terrible. They ended up saying a fuse blew, which blew another fuse. They replaced the fuses and the battery and called it fixed. I knew there was no way it would stay fixed. There's a reason the fuses blew. They disagreed.

Five days later, I was driving, and the transmission had a big thud in the back, ESSC Light, Traction light, and the truck shut down. I was stranded in the middle of one of our most prominent intersections and had to have it towed back to the dealer. The same thing that happened the last time. I'm guessing the wiring harness wasn't correctly fixed, and it's blowing those fuses, but who knows?

That's where we are now.

 

[Moondog023]

First, I love my AT4. I am typing this to help others until GM decides to put out a service bulletin or a recall on the problem. The only reason I put up with this is because I travel a great deal and was able to leave the truck at the dealer for extended periods of time. This is a brand new 2023 1500 AT4, 3.0 Diesel. Ordered in August 2022, received Jan 2023. What happened each time was the craziest thing I ever saw. Usually at a stop sign then accelerate or on a turn at speed suddenly everything in the truck would reset, check engine light, full dash reset, even turned the heater fan on, transmission warnings, on and on and on and on. The first time it happened it scared the hell out of me, left me dead in an intersection in Philadelphia. Horns beeping all around me, and people yelling. Turn it off/on and I can get it to move in a kind of limp mode. I drove it home at 20 MPH, it would only shift to 2nd or 3rd gear. The thing is re-setting all the way.

I get it to the dealer, they call the next day and tell me and I quote "We cant help you. The truck has too many error codes. We reset it and cannot get it to happen again, sorry." They basically ask me to take it home and let them know if it happens again. To make a long story short I had the truck back to the dealer 4 times 1st time, 1 week. 2nd time 2 weeks. 3rd time 3 weeks, 4th time 3 weeks. In between I can only test the truck on the weekends because I travel during the week. They would drive it for hours and hours trying to reproduce the problem, They put a lot of miles on the truck, guessing over 1400. They replaced many, many parts, transmission control module, brake control module, etc. They pulled the truck appart, dash, everything, connected/reconnected as much as they could find. Had a GM local field engineer out several times - tons of recommendations. Still failed after various amounts of time. There is much more to this story, not worth typing.

The problem and the fix:
Bottom line the issue was a wiring harness on the Diesel versions of the AT4, maybe others, that is pulled too tight around the engine block and the alternator bracket. Truck/engine motion wears away the cloth wrap. This happened to me in under 400 miles the first time. Digs into the wires and causes a short. In my case it dug into the white, main communications wire and shorted the communications between all the computers on the truck and it went crazy. The only reason they found it was because they had what I think is a 2023 Denali Diesel with the same issue and through pure dumb luck stumbled across the issue. They then checked mine and found the exact problem. I can understand how it was missed, There is only a pin hole visible and it is buried. To correct the problem they go through the wheel well and because it is a communications wire have a special procedure to repair it.

I am hoping this post helps someone else if they are experiencing strange electrical problems. I was told there are more trucks out there with the same issue. I let them hold onto my truck for an extra few days so GM can come back out, document the problem, examine the repair and re-routing of the wiring harness, then later decide what to do in the future. Pictures below.

So I’m searching online for some answered hopefully. I took my truck in about 2 months ago for an emissions CEL. The computer thought it was putting too much exhaust into the atmosphere. Two days ago I backed out of my driveway to rotate vehicles around. I seen a YouTube video about turning your cargo lights on and your light on the tailgate. For better light at night for hooking trailers up. So I tried this and it made a difference. Turned the cargo lights off then back in. Bam all kinds of service lights from traction control to ABS lights. Called Onstar to get the codes. But before I called them I turned the truck off for about 20 mins. Stated back up all lights were off but the CEL was still on. The codes Onstar gave me was P2297, P25A and C0558. Called my dealer and can’t get in until September 14th. Luckily I have an old 92 Cheyenne that I can drive until then. I don’t know if the truck has a loss in power or not. Not going to chance it until time to take it to the dealer. I say all this and am because I’m curious if this could also be my issue maybe not. But thought it was weird when I pushed the button twice and this occurred. Could of been a coincidence but I’ll have them check the wires after reading this.